This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 arising from an application for a SURVEILLANCE SYSTEM AND METHOD earlier filed in the Korean Industrial Property Office on Feb. 25, 1998 and there duly assigned Ser. No. 5960/1998.
1. Field of the Invention
The present invention relates to a surveillance system and method, and more particularly, to a surveillance system and method in which a surrounding area can be observed using a personal computer equipped with a capture board for capturing an image.
2. Description of the Related Art
An earlier surveillance system comprises a camera installed in a surveillance area, and a closed circuit television (hereinafter referred to as CCTV) with which a guard observes the surveillance area. U.S. Pat. No. 3,825,676 to Ramsden, Jr discloses a Surveillance System using a closed circuit television. Two distinct measurements of a video signal are made. The first measurement is stored. The second measurement is made and compared with the stored measurement. Any difference in excess of a predetermined threshold is indicative of motion of an object within the viewing range. If motion has occurred, an alarm is set off.
U.S. Pat. No. 5,588,067 for a Motion Detection and Image Acquisition Apparatus and Method of Detecting the Motion of and Acquiring an Image of an Object to Peterson et al discloses a device that compares the current image to the previously saved image and calculates a motion vector. If the motion vector is more than a threshold, the current image is saved on microfiche.
However, the prior art does not disclose a pixel by pixel comparison of the luminance differences between a pair of images to determine whether the current image should be saved. Also, there is no indication from the prior art that the time interval between images is adjusted depending on whether or not a current image has just been saved. It is desirable to accomplish these tasks without the use of a video tape recorder so as to save on the amount of equipment used to achieve the image comparison process and the image storage process.
To solve the above problems, it is an object of the present invention to provide a surveillance system and method by which a surveillance area is observed by using a personal computer having an image capture board which is connected to a camera unit and receives images therefrom.
Accordingly, to achieve the above objective, there is provided a surveillance system including: a camera unit; and a surveillance unit connected to the camera unit for storing an image received from the camera unit when the luminance of pixels of the current image received from the camera are compared to the luminance of corresponding pixels of the previously received image and the number of pixels where the change in luminance exceeds a first threshold are counted and it is determined that the number of counted pixels that have a change in luminance that exceeds a first threshold exceeds a second threshold.
To achieve the above objective, there is provided a surveillance method including the steps of: capturing images from a camera at a predetermined time interval; calculating luminance values of pixels in the captured image; comparing the luminance of pixels from the captured image with the luminance of corresponding pixels from the previous image and storing the captured image if the number of pixels in the captured image that have a luminance that differs more than a first predetermined value from corresponding pixels of the previous image exceeds a second predetermined value.